Vapor phase cracking process



Dec. 18., 1934. M B COOKE Er AL 1,984,569

` VAPOR PHASE CRACKING PROCESS v v Fileduarch 12, 1932 'aff CRAC/rnv@ Patented Dec. 18, 1934 l UNITED STTES PATENT OlFFICE VAPOR PHASE CRACKING PROCESS Maurice B. Cooke and Hermann Claus Schutt, New York, N. Y., assignors to Alco Products, Incorporated, New York, N. Y., a corporation of Delaware lApplication March 12, 1932, Serial No. 598,506

6 Claims. (Cl. 1516-66) Our invention relates to a vapor phase crackrapidly on account of the atomized state of the ing process, and more particularly to a process vapors to be cracked. in which oil in the vapor phase is cracked by The charging stock is pumped through suita heated heat carrier gas. able heat exchangers into an accumulator tank The combustion gas has a specific heat of from which it is withdrawn and passed through 5 about .25, whereas refinery gas has a specific the vaporizing coil of the furnace. In this coil heat of about .65. It will be appreciated that, the incoming charging stock is heated to a if refinery gas is used to carry the heat for vaporizing temperature. We vaporize the heated the pyrolytic conversion, it will require a smaller charging stock in a ash evaporator and pass 10 weight of heated gas to treat the given weight the vapors into direct Contact With the heated 10 o f charging stock due to the higher specific heat. gases t0 thoroughly COInmingle lShem- Tlle @Oln- One object of our invention is to provide a mingled gases and VeDOlS Will react due te the process for the cracking of hydrocarbons in the temperature and the pyrolytic decomposition vapor phase by heated gases in which the quanof the vapors will take place to form gasolinetity of gases which have to pass through the like hydrocarbons in the reaction or cracking 15 reaction and fractionating zone is reduced. zone. Inasmuch as the reaction will take place Another object of our invention is to provide rapidly at a temperature 0f 1050 F We DIODOSe a process in which the carrier gas is heated by to stop the reaction to prevent over-cracking indirect heat exchange and in which means are by quenching sprays- It iS t0 be noticed that 2o provided for controlling the temperature of the we provide an increase in cross sectional area in 2o heat carrier gas Within close limits by tempering. Order 120 Prevent the building 11D 0f Pressure;

Still another object of our invention is to The products. after being Chilled. DeSS inte a provide a vapor phase cracking process in which tal' Separatel- The tar leader quenching Oil. iS a heated heat carrier gas is used to supply the drawn through a cooler and Pumped t0 Storage cracking heat and which is flexible of control and may be used fOr fuel Oil- The VeDOlS and' 25 and eilicient in operation. gases are passed through a sectional entrainstill another object of our invention is to proment condenser through a heat exchange evapovide a process in which the reaction is checked relier in Which the heat 0f the DIOdUCtS iS used by means of shock chilling in order to prevent t0 vValJOl'iZe Water t0 fOrm Steam and then inte over-cracking. a fractionating tower. The condensate from the 30 Other objects of our invention will appear entrainment condenser collects in suitable pockfrom the following description. ets and may be passed either into the separator The gure shows a diagrammatic view of one 01 inte a -fleetienating tower depending upon embodiment of the process of our invention. their nature and ellel'eeterl In general, our invention consists in burning The Tefllul condensate from the fraetionating 35 fuel in a furnace. If desired, a surface comtower is Withdrawn and pumped through a bastion bumef may be used to generate hat cooler in order to'reduce the temperature theregases of combustion. The radiant heat generof to rendr 1t smtable as a quenchmg-med1umated within the furnace is employed to heat After passmg through the cooler' it 1S passed 40 the hydrocarbon on to be cracked. Renew through'the sprays in order to be used in the 40 chilling zone. A portion oi the reux condensate of the fractlonating tower 1lililiay ldiverted into the accumulator for recyc g. e vapors We tower are cooled and passed into a separator provlfie means for mtroducmg a' quantlty of from which the water is withdrawn. The concarbon, doxlde and Steam at spaced points in ,densate is withdrawn from the separator as gasthe coilin order to control the outlet teml oline and passed to storage The uncondensed perature and the pyrolytic reaction of the heated gases from the separator are compressed and gaSeS- We have found that 9 temperature 0f cooled and passed into an absorber where they 50 about 1500 F. will give the best results. At this are mixed with a lean oil asin a gasoline abtemperature, the heated gases when admixed sorption process. with the oil vapors, will result in a mixture A fat oil drawn from the bottom of the abtemperature of about 1050 F. to 1150" F.' at sorber is passed into a steam still to recover the which temperature the cracking will take place gasoline fractions. The tlxed gas is passed into 55 gas is withdrawn lfrom the gas main and passed in indirect heat Lexchange with the ilue gases burner of the 5 and go past the coil 6 and out .through the ue connection 7 and the chimney 8. It is to be understood that, while I have shown coils, any

. suitable type of pipe still equipment may be employed.

A branch line 9 supplies refinery gas to the flue heat exchanger 10 in which the reilnery gas passesl in heat exchange with the gases passing through the flue 7. After being preheated, the reflnery gases pass through line 11 and into coil 6 through which they flow in heat exchange with the hot combustion gases. A" connection 12 supplies carbon dioxide under the control of valve 13 for varying the quantity of gases and has a further function of acting as areaction and a temperature control. If the temperature of the heated gases entering the mixing zone be too high, by opening valve 13 the temperature may be reduced and, on the other hand, if the temperature of the gases entering the mixing zone be too low, the valve 13 may be partially or entirely closed. Line 14 controlled by valve 15 supplies steam to the coil 6. The steam acts both as a reaction controlling and a tempering agent and as an additional heat carrier due to its high.

specific heat. The heat-carrier gas leaves the coil 6 and passes into the mixing zone 16 at a temperature of about 1500 F. The products leaving the coil 6 will be hereinafter referred to as the heat-carrier gas and will include the refinery gas, the carbon dioxide and whatever steam may be present.

Hydrocarbon oil, being charged through line 17, is pumped by pump 18 through line 19 through heat exchanger 20, through line 21, into accumulator 22. From the accumulator 22 the fresh feed and recycle oil are pumped by pump 23 through heat exchanger 24 and are pumped through line 32, it being understood that valves 33 and 34 are open and valve 35 is closed or partially closed. The charge passes from line 32 through the tubing 36 of the sectional entrainment vcondenser 37 and leaves said condenser through line 38 passing through valye 33 into line 39, through the vaporizing heating coil 4. The heated charging stock leaves the coil 4 through line 41 and passes into the flash evaporator 42. The unvaporized oil from the flash evaporator may pass through line 43, through valve 44, through line 45, through lcooler 49, where it is pumped by pump 50 to storage as fuel oil, or it may be returned to the accumulator for recycling. 'I'he vapors from the ash evaporator will pass through line 51 and be discharged into a mixing zone 16. Valve 51 controls the vapor flow. a

The hydrocarbon vapors entering the mixing zone through line 51 will be -commingled and mixed with the heated heat-carrier gas to form a` mixture'having a resultant temperature of about 1100 F., and cracking or pyrolytic decomposition will take plac'e rapidly.

As cracking takes place, the volume of the products will increase and, in order to prevent ueeaeea the building up of pressure, a cracking chamber of progressively increasing volume is provided.

Inasmuch as the cracking will take place very rapidly, at the temperature of 1050 F. we resort to shock chilling or quenching to reduce the temperature of the products of reaction from 1100 to 700 F. We do this by means of oil prays 53, 54, and 55, oil spray 55 being located in the tar separator 57. The temperature of 700 is low enough to prevent any further reaction and high enough to permit the distillate to escape in the vapor Vstate, into the fractionating tower. The heavy, tarry fuel oil, however, will accumulate in the bottoms of the separator 57. These heavy bottoms are Withdrawn through line 58 which joins with line 45 and permits the fuel oil bottoms to bepassed'through the cooler 49 to fuel oil storage.

The vapors and gases from the tar separator 57 pass overhead through line 59 into a sectional entrainment condenser 37, whence they will pass in counterflow relation to the incoming charging stock which is passing through tubes 56. The hot vapors will be cooled considerably by the incoming charging stock which in turn will be heated. The entrainment condensate is allowed to`l collect in compartments 60, 61, and 62. The condensate may be withdrawn from the respective compartments and selectively passed into the separator or fractionating tower through lines 63 and 64 respectively. The condensate may be supplied as desired by means of valves 65, 66, 67 and 68, so that all or part of the condensate collected in the sectional entrainment condenser 37 may be passed'to either the separator or the fractionating tower as desired and depending upon the nature of the condensate. The vapors and gases leave the sectional entrainment Vcondenser through line 69 and pass into the fresh water evaporator 25. Fresh water is admitted through valve controlled line 26 and passes through the tubes 27 of the fresh water evaporator 26 in heat exchange relationship with the hot vapors entering through line 69 from the sectional entrainment condenser. The heat of the vapors will be suilicient to convert the water into steam which leaves the tubes 27 through line 28 which passes into line 14 for use as injection into the coil 6 as heretofore described. The vapors thus further cooled are withdrawn through valve controlled line 29 and pass into the fractionating tower 70. The condensate formed in the bottom of the evaporator 25 is withdrawn through valve controlled line 30 and likewise pas's into the fractionating tower 70.'V

The reflux condensate from the fractionating tower is withdrawn through line 7l and passed partly through heat exchanger 24, through line 72, through cooler 74 and into line 76, which terminates in a manifold for the quenching sprays. The quenching oil leaves line 76 through valve controlled lines 77, 78 and 80. A portion of the reflux condensate from the fractionating tower is diverted through valve controlled line 81 and allowed to pass into the accumulator for recycling.

The vapors and gases from the fractionating tower passes through line 82, through heat exchanger 20, through cooler 83, through line 84 into separator 85. Water from the bottom ofthe separator is withdrawn through line 86. The gasoline-like hydrocarbons are withdrawn through line 87 and passed to storage. A por'- -many advantages.

tion of the oil is withdrawn through line 98 and pumped by pump 99 through line 100 into the fractionating tower 70 as reflux. The gas from the separator will contain a quantity of gas rich in gasoline-like hydrocarbons. Accordingly, I propose to withdraw it through line 88'and compress the gas in compressor 89, pass it through cooler 90, through line 93 and into the gasoline absorption tower 94 where it is scrubbed by lean oil entering through line 95. The iixed gas is withdrawn through line 96 into gas main 1. 'I'he fat oil from the bottom of the absorption tower` 94 is withdrawn through line 97 and passed to a steam still for the distillation therefrom of the gasoline-like 'hydrocarbons.

It will be appreciated that my process has By using a heat carrier gas having a higher specific heat than ordinary combustion gases, I am enabled to crack in the vapor phase by hot gases of combustion and at the same time avoid excessive size of fractionating and absorption equipment due to the fact that a small quantity of gases will be necessary tocrack a given amount of charging stock. We provide an efficient means for cracking hydrocarbon vapors by heated gases and, at the same time, we ,provide a process which is flexible of control. The thermaleiciency of our process is exceedingly high. The temperature of the'v heated heat carrier gas, the temperature of the quenching oil, and hence the temperature of the reaction may be controlled within closelimits.

We are enabled by our process to crack hydrocarbon oil in the vapor phase and obtain a gasoline-like hydrocarbon suitable for use as a motor fuel and having an exceedingly high antiknock value. We may use a portion of the gas formed in our process for other purposes where gaseous fuel may be needed and as the carrier gas. It will be noted that the cracking .reaction takes place in the pure .vapor phase, it being impossible for any hydrocarbon oil which is not in the vapor form to be present. This insures the absence of the danger of the formation of coke or carbon deposits within our cracking zone. It will be understood, of course, that suitable lagging is provided throughout the piping and the piece-of apparatus used in our process to prevent the loss of heat by radiation.

It will bel understood that certain features,v

sub-combinations and operations are of utility and may be employed without reference to other features and sub-combinations. This is con.- templated by and is within thel scope of our claims. It is further obvious that various changes may be made in details -within the scope of our claims without departing from the spirit of our invention. It is, therefore, to be understood that our invention isnot to be limited to the specic details shown and described.

By this method of cracking hydrocarbons in the vapor phase, in which the hydrocarbons are combined with the combustion gases, the latter being maintained at selected, controlled temperatures of reaction, a motor fuel having a high octane number and high antiknock value is obtained. The process eliminates parasitic cracking which accompanies conventional cracking methods, in which the hydrocarbons are converted in tubular containers and heated by external circulation of the combustion gases thereabout. The intimate mixture of the combustion gases with the hydrocarbon vapor produces a distribution of heat impossible with the conventional tubular crackingprocesses.

Having thus described our invention, what we claim is:

1. The process of converting hydrocarbons in the vapor phase into gasoline-like hydrocarbons of lower molecular weight including the steps of heating the hydrocarbon oil to lbe converted in an elongated confined stream, ashing said heated oil into vapors in an evaporating stage, separately withdrawing the vaporized and unvaporized portions from said evaporating stage, simultaneously with said vaporizing steps heating a heat carrier gas by indirect heat exchange, controlling the temperature and reaction of said heat carrier gas by injecting cooler inert gases thereto during said gas heating step, commingling saidheated heat carrier gas with the hydrocarbon vapors withdrawn from said evaporating stage in a zone entirely free of liquid to permit pyrolyticdecomposition of said hydrocarbon vapors to take place whereby gasoline-like hydrocarbons having a lower molecular weight are produced.

' 2. 'I he process of converting hydrocarbons in the vapor phase into gasoline-like hydrocarbons of lower molecular weight including the steps of heating the hydrocarbon oil to be converted, in an elongated confined stream, flashing said heated oil into vapors in an evaporating stage, Vsimultaneously heating a heat carrier gas by indirect heat exchange, controlling the temperature to which said gas is heated and the pyrolytic reaction by admixture therewith during said gas heating step, of cooler inert gases in order to bring the exit temperature of said carrier gas to about 1500" F., admixing the vapors withdrawn from the evaporating stage with said heated heat carrier gas whereby 'the temperature of the mixture will be substantially between 1050" F. and 1100 F., allowing a. pyrolytic decomposition of said vapors to take place in a zone entirely free of liquid whereby gasoline-like hydrocarbons having a lower molecular weight are produced, stopping said reaction by spraying oil after the reaction has progressed to a desired Aextent whereby overcracking is prevented.

3. The process of converting hydrocarbons in the vapor phase into gasoline-like hydrocarbons of lower ymolecular weight including the steps of heating the hydrocarbon oil to be converted in an elongated confined stream, ashing said heated hydrocarbons into vapors in an evaporating stage, simultaneously heating a heat carrier gas by indirect heat exchange, controlling the temperature to which said gas is heated and the pyrolytic reaction by admixture therewith during said gas heating step of cooler inert gases in order to bring the exit temperature of said carrier gas to about 1500 F., admixing the vapors withdrawn i'roni the evaporating stage with said heated heat carrier gas whereby theV Oil.

el Leegte@ 4. The process of converting hydrocarbons in the vapor phase intogasoline-like hydrocarbons of lower molecular weight including the steps of heating the hydrocarbon oil to be converted in an elongated conned stream, a'shing said heated hydrocarbons into vapors in an evaporating stage, simultaneously heatingv a heat carrier gas by indirect heat exchange, controlling the temperature to which said gas is heated andthe .said hot gases and vapors after the reaction has progressed to Y a desired extent whereby overcracking is prevented, fractionating the products of reaction and withdrawing the reflux condensate from the fractionating stage for use as a quenching oil, withdrawing the vapor and gases from the fractionating stage, cooling said vapors and gases, withdrawing the condensate formed in the vapor and gas cooling stage and subjecting the uncondensed products to gasoline absorption treatment.

5. The process of converting hydrocarbons in the vapor phase into gasoline-like hydrocarbons of lower molecular weight including the steps of heating the hydrocarbon oil to be converted in an elongated coni-ined stream, hashing said heated hydrocarbons into vapors .in an evaporating stage, simultaneously heating a heat carrier gas by indirect heat exchange, controlling the temperature to which said gas is heated by admixture therewith during said gas heating step of cooler inert gases in order to bring the exit temperature of said carrier gas to about1500 F., admixing the vapors withdrawn from the evaporating stage with` said heated heat carrier gas whereby the temperature of the mixture will be substantially between 1050" 'F. and 1100 F., allowing a pyrolytic decomposition of said vapors to take place in a zone entirely free of liquid whereby gasoline-like hydrocarbons having a lower molecular -weight are produced, stop- Y vapors and gases, withdrawing the condensate formed in said vapor and gas cooling stage,

' subjecting the uncondensed products to gasoline 1 absorption treatment, and withdrawing the ilxed gases from the gasoline absorption operation for use as the heat carrier gas and as .a fuel* gas.

6. The process of converting hydrocarbon oils into gasoline-like hydrocarbons of lower molecular weight including the steps of heating the hydrocarbon oil to be converted, ilashing the heated oil into vapors vand unvaporized oil in an evaporating stage, separately withdrawing the vapors and unvaporized oil from said evaporating stage, simultaneously with said vaporizing steps heating a heat carrier gas in an Aelongated confined stream, commingling said heated heat carrier gas with hydrocarbon vapors withdrawn from said evaporating stageto permit a pyrolytic decomposition of thevapors to take place whereby gasoline-like hydrocarbons are formed and controlling the reaction by governing the temperature of the heated heat carrier gas by injectinga cooler gas or vapor into the elongatedconned stream while said stream is being heated. I

MAURICE B. COOKE. HERMANN CLAUS 

